(1) Field of the Invention
The invention relates to a device for grinding an external sleeve surface on a rotationally symmetrical body, in particular for grinding a roll on a paper machine, comprising a support frame, displaceable along the external sleeve surface of the body to which at least one driven belt grinder is fixed and several pivoted running rollers, laterally spaced in the circumferential direction of the body, resting on the external sleeve surface of the body.
(2) Description of the Prior Art
A belt grinding apparatus of prior art is familiar from WO 98/03304; this apparatus possesses a support frame in which a belt grinder is arranged. Two rollers are arranged on the side next to the belt grinder on the free end of the U-shaped support frame; these rollers are assigned to the body to be machined and are in contact with the surface of the roll. A further linkage is provided on the side next to one of the two rollers, the linkage possessing two rollers resting on rolls. One of the two rollers runs on the surface of a roll which is located at a distance from the roll to be machined. A drive device is arranged on one side of the support frame facing away from the rolls, so that the belt grinding apparatus can be moved along the outer external sleeve surface of the roll. The belt grinder is pressed against the roll to be machined by means of a pneumatic servo device in such a way that the servo device presses against the intrinsic weight of the support frame.
A device of this kind has proved to be disadvantageous in that reliable grinding and machining of the external sleeve surface of the roll cannot be guaranteed since the contact force is limited due to the arrangement of the device on the roll, which means the belt grinder can only be pressed against the external sleeve surface of the roll to an inadequate extent. As a result, all that can be achieved is to clean and polish the external sleeve surface of the roll.
The contact force generated by the servo device is insufficient, since the very light weight of the device is inadequate for contour grinding. However, the device is not guided in the axial direction, so that control of the device is imprecise and consequently no support is provided.
Furthermore, the device of prior art can only be used if there is a second, adjacent roll, because this device requires a back-up roller which is in contact with an adjacent roll. Otherwise, namely, the belt grinding apparatus would not be held against the external contour of the roll, but would slide instead. However, the laterally projecting framework constructions which prevent the belt grinding apparatus from slipping in this manner take up a lot of space, so that before the roll can be machined it is necessary to make sure that the device for grinding off material can be moved freely along the external contour of the roll. Under certain circumstances, this means that the rolls used in paper mills have to be removed, or at least that all other components in the area around the rolls have to be removed. However, the standstill time of the rolls must be kept as short as possible during machining since these paper machines must produce paper round the clock in order to operate profitably.
The purpose of the present invention is therefore to create a device for grinding an external sleeve surface of the aforementioned type, by means of which rapid and positionally accurate grinding of the external contour is guaranteed without the need to afford free access to the rotationally symmetrical body to be machined in a paper mill. Furthermore, it should be possible to move the device along the body straightforwardly and with positional accuracy in the direction of the longitudinal axis of the body.
In accordance with the present invention, this task is undertaken in that a fixed thrust bearing is assigned to the external sleeve surface to be machined, in that a calibration device is inserted in between the thrust bearing and the support frame connected to the latter and braced against the thrust bearing, and in that the contact pressure acting on the external sleeve surface and/or the advance movement of the belt grinder according to the given unevenness of the external sleeve surface and/or the measured eccentricity of the body can be adjusted using the calibration device, or that a support member is mounted on the support frame and that the free end of the support member is in movable contact with a thrust bearing arranged at an interval from the body.
Further advantageous embodiments of the invention are described in the subordinate claims.
In the first alternative of the device in accordance with the present invention for grinding down the external sleeve surface of a rotationally symmetrical body, it has proven to be beneficial for the support frame of the device to be braced against a thrust bearing, so that the advance movement and the contact pressure of the belt grinder can be applied in a defined manner since the force needed for advancing the belt grinder is absorbed by the thrust bearing. By this means, it is guaranteed that the grinding process can be performed quickly and reliably since the contact pressure and advance movement of the belt grinder can be set according to the given unevenness of the external sleeve surface.
Normally, it is possible to employ the shafts present in paper mills as the thrust bearing; these shafts being otherwise used for deflecting and drying nonwoven material and the support frame is braced against them. Possible geometrical discrepancies between the longitudinal axis of the shaft and the longitudinal axis of the rotationally symmetrical body can be compensated for by using the calibration device to alter the position of the support frame in relation to the external sleeve surface of the body. However, it has proven to be advantageous to have the configuration of the shaft identical in the most part to the geometrical track of the body to be machined, at least with regard to their common bowing along the longitudinal axis, with the result that compensation for faults is often not required.
If there is no thrust bearing immediately available, this can easily be provided by means of a tube or the like clamped between the support for the body to be machined. There is no need for extensive and time-consuming conversion or dismantling work because the grinding device is compact and therefore takes up little space.
In the second alternative of the device in accordance with the present invention, the contact pressure needed for grinding the roll is exclusively generated by means of the weight of the device which is supported against the external sleeve surface of the roll by means of running rollers. The evaluation and control unit is connected to the servo devices which lift or lift off the running rollers in such a way that the contact pressure of the belt grinder can be varied between the value zero and approximately the weight of the device.
The device is held against the external sleeve surface of the roll because the weight axis of the device runs in line with the weight axis of the roll and because the torque generated by the rotation of the roll and/or the belt grinder is braced against the thrust bearing arranged at an interval from the body. As a result, no other support devices are required.
Consequently, there is no need for dismantling work on the roll in order to be able to grind it down. Instead, the device can be placed onto the roll without any delay. The roll can also be driven by means of the motor attached to the device, thereby guaranteeing a very rapid and uncomplicated operating method of the device along the longitudinal axis of the body.
However, it is also theoretically possible for the device to be moved along the longitudinal axis of the body as a result of the rotation of the body if at least one running roller is oriented at an angle to the longitudinal axis.